1. Field of the Invention
The present invention relates to a secondary battery device and charging apparatus. More particularly, the present invention relates to a secondary battery device equipped with an even number of secondary batteries and one or more temperature detecting elements and its associated charging apparatus.
2. Background of the Invention
Ni-Cd (Nickel Cadmium) and Ni-MH (Nickel Hydrogen) batteries are well known as secondary batteries. One particular aspect which is well known is that the voltage for Ni-MH batteries is 1.2 V, which is the same as for Ni-Cd batteries, but Ni-Cd batteries have only half the capacity of Ni-MH batteries. Ni-MH batteries are also capable of rapid charging and large current discharge.
The performance of Ni-MH batteries is weakened if they reach a high temperature during charging, i.e. if the temperature of the external wall becomes greater than 66.degree. C., for example.
It follows that if a Ni-MH battery generates heat and reaches a high temperature during charging due to abnormalities in the charging apparatus and so forth, it is necessary to halt the charging. Also, in the case where the batteries have reached a high temperature before the start of charging due to neglect inside a car in direct sunlight in the summer, it is necessary to halt charging directly after the start or not to start charging at all.
With equipment such as compact stereo headphone cassette tape players and so forth, where the power consumption is quite small, just one Ni-MH battery is sufficient for operation. However, with equipment such as portable telephones and cameras with built-in VCRs, the power consumption is comparatively high and it therefore becomes necessary to use two or more Ni-MH batteries connected together in series.